Fluid heat exchange apparatus



FQTW 3%? R. M. HARDGROVE FLUID HEAT EXCHANGE APPARATUS e Shets-She et 1 Filed Nov. 19, 1958 cob o j v!. O0 0 0 0 0 OO O 00 O0 O0 O0 O0 O0 O0 O0 0 0 OO O O O 0 0 O O O O W, 0 w w o w o 0 w 0 we 0 \O m 0 0 000 O 03 o 0 m 0 0 o 0 O 0 0 O O O w o 0 0 wow 0 0 0 0 0 0 m m o 0 0 4 0 0 0 0 o o wowow 0 0 wwnovwm 0000 2% INVENTOR. Ralph Mfiardyrow/e ebo 3, 1%2. M. HARDGROVE v fi FLUID HEAT EXCHANGE APPARATUS Filed NOV. 19, 1938 6 Sheets-Sheeft 2 Fig 4 INVENTOR. rdgrvz/e R. M. HARDGROVE FLUID HEAT EXCHANGE APPARATUS Filed Nov. 19, 1958 6 Sheets-Sheet 3 I IN VENT OR. RaZpiz MHamymVe ooooooocooooo u n w 342 R. M. HARDGROVE v FLUID HEAT EXCHANGE APPARATUS Filed Nov. 19, 1938 6 Sheets-Sheet 4 Fig 4 9 5 OOODOOOOOOOOOOOOOOO 0000000000 0000000000 0000000000 m 2, n I n w 5 III 1 fin WH H H W M n H i H i 00 v INVENT OR. Ralph M Hardyroz/e 9 i942 M. HARDGROVE a fi FLUID HEAT EXCHANGE APPARATUS Filed Nov. 19, 1958 6 Sheets-Sheet 5 O O 0 O O O O O O O O O 0 0 0 [30 J52 v f BY Ralph MHa rayrm/e' ATTORNEY.

Feb 3, 3942.,

R. M. HARDGROVE zmww FLUID HEAT EXCHANGE APPARATUS 6 Sheets-Sheet 6 Filed Nov. 19, 1958 INVENTOR.

Ralph MHamymI/e ATTo RNEY.

Patented Feb. 3, 1942 UNlTED STATES PATENT OFFICE ramp lunar nxcnaxas arrana'rus Ralph M. flal'dfl'ove, weaned, N. a, assignor to The Babcock & Wilcox Company, Newark, N 1., a corporation of New Jersey Application November 19, 1938, Serial No. 24am 2 Claims. (01. 122-235) V This invention relates -to fluid heat exchange apparatus in which there is a natural circulation of fluid through a system of tubes connected to a fluid chamber.

The invention will be considered as exemplified by a water tube steam boiler having a bank of upwardly extending tubes connecting a lower drum to an upper steam and water drum, the flow of water being downward through some or the tubes to the lower drum while steam and water flow upward through other tubes to the steam and water drum. The water is heated by furnace gases sweeping the tubes.

An object of the invention is to prevent damage to the tubes of such apparatus by reason of overheating due to defective circulatory conditions. The invention aims to prevent such damage without the use of external downcomers and without the use of baflles to exclude some of the tubes from contact with furnace gases.

To prevent overheating of the tubes of such boilers a flow of fluid, usually water or a mixture of water and steam, must be maintained through the tubes. When the flow is inadequate stagnation results and the tubes will not be sufiiciently cooled internally.

The tubes of water tube boilers of the bent tube type have been usually of the same diameter in order to give manufacturing advantages, and the tendency is for the front tubes of a bank to be risers and the rear tubes downcomers, when furnace gases transversely sweep the tubes from front to rear of the bank. However, there has been no fixed or certain division of the bank of tubes into two sets, and experience has shown that some tubes of such a bank may at one time (and under certain load or firing conditions) be risers, and, at other times and under different conditions, be downcomers, and with this tendency, and circulation uncertainty as to whether the flow in certain tubes be an upiiow or downflow, there has been neutralization of flow andcirculatory stagnation. This has resulted in the formation of steam pockets, causing the tubes to have high internal resistance to heat transfer. This has resulted in such overheating and consequent tube damage that it has often been necessary to shut boilers down until the damaged tubes could be replaced. Such shut-down periods are particularly undesirable difficult it is to make certain that enough of the tubes will function as downcomers to provide the water required to keep the riser tubes wet at their upper ends and. at the same time, to prevent stagnation in tubes that might be damaged by overheating thereby.

This invention overcomes these diflieulties, and, in so doing, involves the use of large diameter tubes subjected to the same furnace gases as adjacent small diameter riser tubes.

The large diameter tubes thus set in a tube bank of tubes of smaller diameter will carry down all the water required by the riser tubes no matter how intensely heated. The boiler circulation is thus stabilized and overheating of tubes prevented.

Another object of the invention is to strengthen the whole structure without costly steel framework when the large diameter downcomers constitute drum supports. The downcomers, being more rigid and stiffer than the smaller tubes of the bank, may be utilized as the major support members for the upper drum from the lower drums. This is especially important-in ships. With this arrangement, the smaller tubes may flex as thermal expansion requires, without imposing undesirable limitations of strength requirements and without other supports for the boiler. 1

In the operation of the above indicated type of boiler there is a flow of water horizontally in the upper drum from regions in which riser tubes discharge steam and water into the drum (or in which separation occurs) to regions where the downcomers conduct water from the drum. Such flows, which may be longitudinally of the drum, impose level differences to maintain them,

and such differences are substantial when the in high capacity steam generating installations,

operating at high pressures and temperatures.

The higher the steaming capacity of the tube bank, arising from a maximum flow of high temperature furnace gases across it, the more distances between those regions are excessive. Thus'water level conditions become unstable and good boiler operationdifllcult. The present invention overcomes this difficulty by such disposition of the large diameter tubes that the paths of such flows are as short as possible. The

characteristic whereby the downcomers may be for the superheater. In marine boilers of this class, it is the practice to locate the superheater in front of the main tube bank and behind rows of tubes forming a water screen in a position where the gases are of high temperature and there must be supports for the superheater. If these supports are located externally of the gas pass to avoid overheating of the supports, additional weight and expense is incurred. When large diameter tubes are located intermediate of first and last rows of tubes between the drums, they may be used as water cooled supports for the superheater and thus the superheater is supported independently of the tubes of the bank and screen, being kept cool by the downcomer flow of water in them. No other superheater support is necessary, but in some cases the external headers may be used to support the superheater in part while the large downcomer tubes provide the rest.

Other objects of the invention will appear as the accompanying description proceeds, the invention being described-with reference to the drawings which indicate preferred embodiments of the invention.

In the drawings:

Fig. l is partly a vertical section and partly an elevation of a steam generator constructed in accordance with thi invention;

Fig. 2 is a transverse horizontal section through a bank of tubes such as that shown in Fig. 1 of the drawings; I

Fig. 3 is a view similar to Fig. 1, showing a somewhat modified steam generator;

Fig. 4 is a transverse section through the superheater and the bank of tubes of the Fig. 3 generator;

Fig. 5 is a view somewhat in the nature of a vertical section through a steam generator which constitutes an additional embodiment of the invention; v

Fig. 6 is a horizontal section taken on the line 66 of Fig. 5;

Fig. 7 is a vertical section through a bent tube boiler in which the teachings of this invention are utilized;

Fig. 8 is a partial transverse section on the broken section line 88 of Fig. '7

Fig. 9 is a vertical section indicating another type of steam generator, this view being taken on the section line 9-9 of Fig. 10;

Fig. 10 is a plan of the steam generator indicated in Fig. 9;

Fig. 11 is an enlarged detail view of a part of the superheater construction of the Fig. 3 boiler; and

Figs. 12 and 13 are detail views of parts of the boiler shown in Figs. 3, 4 and 11.

The steam generator shown in Fig. 1 of the drawings includes the steam and water drum l0- connected by downwardly diverging banks of tubes to the water drums l2 and I4. The drum I2 is directly connected to the drum [0 by a bank of tubes l6, rows of tubes I8, and a middle group of tubes 20, the tubes l8 comprising a furnace screen or narrow front bank. On the opposite side of the furnace 22 the drum l4 may be connected to the drum It by similar groups of tubes.

The furnace 22 is fired at high rates by a plurality of burners 24, and furnace gases sweep transversely of the tubes extending upward to the drum l0, and then pass to the separate out- 4 in Fig. 2 of the drawings. The tubes of the screen l8 are steam generating tubes, or risers, discharging steam and water into the dmm l8. Likewise; the tubes 88 and 82 of the middle group 20 are risers, but adjacent the latter in the same row and distributed in three groups across the gas pass are the large diameter tubes 84, I6, and 38 which act definitely as downcomers. They are distributed across the width of the gas flow and the length of the drum so as to make the horizontal flow of water within the drum short and to afford adequate structural support for the drum Hi from the drums l2 and I4 which are carried on saddles as shown. These larger tubes 34, 36, and 38 are subject to furnace gases which are of the same temperature as the gases which contact with the tubes 88 and 82 in the same row, but by reason of the considerably larger diameter of the tubes 84, 86, and 88 they act to conduct water downwardly from the drum ill to the drum 12 even when the smaller tubes in the same zone are acting as risers.

The steam generator indicated in Figs. 5 and 6 of the drawings includes a single upper steam and water drum 40 connected by upright tubes to two lower water drums 42 and 48. The latter are disposed toward theopposite sides of the horizontal gas pass in which the main portions of the tubes are located. Hot gases pass from the inlet 58 across the upright tubes and then to the gas outlet 62. As shown, there is a front bank of steam generating tubes 54, a superheater 56, and a rear bank of tubes 58. The latter are all of the same diameter except for the tubes of the group 60. This group is shown as consisting of twelve tubes of much greater diameter than the adjacent tubes of the bank 58 so that'they will definitely act as downcomers. The latter tubes are symmetrically arranged so that they maybe expanded into the upper drum 40 at their upper ends while half of them are expanded into the drum 42 at the lower part of the boiler. The remainder of these tubes are expanded into the other lower drum 48.

The superheater 56 consists of U-tubes communicating with a superheater inlet header 66 and an outlet header 68 located below the level of the flowing hot gases. The former is directly connected with the steam space of the drum 48 by a conduit 10.

The steam generator indicated in Figs. '7 and 8 of the drawings includes a furnace l2 fired by burners I4 and 16 and having its walls defined by water tubes connected into the boiler circulation, some of these tubes being directly connected to the upper drum 18. From the furnace the combustion gases pass across a screen formed by the spaced tubes 86, 82, 84, and 86. These tubes are shown as directly connecting the submerged drum 88 with the upper drum I8.

After passing across the tubes 86 the furnace gases from the furnace 12 contact with the tubes of the superheater which are suspended in the path of the furnace gases. The superheater receives steam from the steam and water drum 92 through the saturated steam supply tubes 94 and the superheater inlet header 85.

After passing across the superheater the gases in the Fig. 7 boiler pass across the tubes of the rear bank 96 and thence through the air heater 88 to a flue. The furnace gases are at such high temperatures in contacting the tubes of the bank 86 that some of the tubes I08 of that bank act as steam generators or risers. However, the bank of tubesv 96 includes groups of downcomer tubes some of which are shown at I82. These tubes e from the drum positions in the bank 88, and longitudinally'of the drums 88 and 82.

The steam generator indicated in Figs. 9 and 10 of the drawings includes a steam and water drum 118 connected by upright tubes to ajsubmerged drum 112. Hot-gasesfrom the furnace 114 pass through an outlet between the boiler setting wall 118 and the baflle 118. Across thisgas flow path there are arranged five rows of relatively small diameter steam generating tubes 128. The sixth row of tubes located at the rear of these five rows includes the risers 122 which are preferably of the same diameter as the tubes in the first five rows and are arranged in groups of two. Between these successive groups there are large diameter tubes '124 which, though exposed to the furnace gases at'the same temperature as the gases contacting the risers 122, act as downcomers. It will also be'noted that the tubes 124 are distributed uniformly across the bank of steam generating tubes between the wall 118 and the baflle 118 so that the water fiow within the drum 118 from thetops of the risers to the tops of the downcomers is shorter than it otherwise would be. V

In the modification shown in Figs. 9 and 10 and positioned rearwardly of the above described steam generating tubes is a superheater 138 receiving steam through the conduit 132 from the steam and'water druni 118. Beyond the superheater the gases turn around the rear edge of the bafiie H8 and pass across tubes arranged within the second gas pass 188. They make one more turn in moving from this gas pass around the forward edge of the baflie 182 and then sweep transversely of the tubes of the gas pass i134, and

112. Other wall tubes 1'18 extend along the wall 172 from a lower header to the drum 118.

r3 alongside the boiler header is shown disposed setting and in parallelismwith the tubes of the;

bank222.

As indicated in Fig. 4 of the drawings the header 284 is connected by relatively small diameter superheater tubes 288 to an outlet header 238. The latter is shown as positioned alongside the inlet header 284 and arranged in parallelism therewith. From the outlet header 238 the superheated steam passes to a point of use.

As further indicated in Fig. 4 of the drawings the superheater tubes are in the form of loops. Each tube presenting a loop 248 near the wall 242 of the boiler. At the opposite wall 244, the superheater tubes are supported by the headers 284 and 238, and the looped ends of the superheater tubes are supported by water tubes 248 and 248 of relatively large diameter. The latter are shown arranged in groups of two near the opposite sides of the tube banks. These large diameter tubes are in communication with the upper and lower drums, and although they are exposed to furnace gases at higher temperatures Fig. 3 of the drawings illustrates a marine boiler in which a steam and water drum 218 is connected with the lower drums 212 and 214 by banks of tubes. The drums 212 and 214 are bottom supported upon saddles or pedestals 218 and 218 and the drum 258 is supported from the drums 2 12 and 218 through some of the tubes which connect those drums. A bank of tubes 228 and screen tubes 222 are shown connecting the drum 218 to the drum 212, and it will be understood that a similar arrangement of tubes connects the drum 268 with the drum 218.

A furnace 226 is located between the upwardly converging screen rows and banks of steam generating tubes and its burners 226 are preferably disposed in a furnace wall which is normal to the longitudinal axes of the drums. When a comparatively large number of burners is used, and supplied with a fuel oil, the furnace is fired at high ratings, and high steam generating capacities are attained. The furnace gases pass from the combustion chamber 228 across the steam generating tubes to outlet fiues 228 and 238. Such auxiliaries as'economizers and air heaters may be disposed in these flues and the operation of the apparatus may be controlled by dampers positioned in the fiues. Saturated steam passes I 218 through an offtake conduit 232 to a superheater inlet header 234. This than the gases contacting with the tubes of the bank 228, they definitely act as downcomers on account of their increased diameter. These tubes are arranged transversely of the rows of superheater tubes as shown, and between the tubes 248 there are clamped metallic plates 258 and 252, together with the metallic saddles 254 and 258. shown in better detail in Fig. 13 of the drawings. They are held in compact relationship by the clamping devices 258. This entire assembly constitutes an inclined water cooled beam or column independent of the other tubes of the boiler and disposed across the gas pass as an heat absorber.

The plate members 258 and 252 are parallel to the water tube beam and are protected from overheating by the good thermal connection made by the clamping members and the interposed saddles 254 and 258. The circulation of water through the beam or column keeps the metal temperature of its parts at properly low values. Excessive distortion'of the plates 258 and 252 due to differences of temperature at the edges of the plates is prevented by slots 288 and 282 which are shown in Fig. 12 of the drawings as extending inwardly from the edges of the plates remote from the tubes 248 and 248.

The clamp members 284 and their associated parts are maintained at desired elevations along the tubes 248 by lugs 288 which are welded to those tubes. Thus the vertical gravitational load of the superheater is taken at one end by the tubes 248. at a plurality of positions along those tubes, dependent upon-the positioning of the lugs 288. A similar support for the other end of the superheater loops may be provided by the tubes 248.

This application is a continuation in part of applicant's co-pending application, Serial No. 38,345, which has eventuated into Patent No. 2,165,258, dated July 11, 1939.

I claim:

1. In fiuid heat exchange apparatus, an upper drum, a lower drum, a bank of fluid conducting tubes forming risers connecting the drums and swept transversely by furnace gases, said risers being arranged in rows transversely of the gas stream, and a plurality of other fluid conducting tubes arranged in at least one of said rows and providing downcomers each of which is of an inside diameter at least 50% greater than that of the risersand of uniform fiow area throughout its length, said downcomers Joining said drums and being disposed intermediateiy of said bank (front to rear) andbeing swept by the furnace gases in a manner similar to the risers.

2. In fluid heat exchange apparatus, an upper 5 drum, a lower drum, a bank or fluid conducting tubes forming risers connecting the drums and swept transversely by furnace gases, said risers being arranged in rows transversely of the gas 

